Various information processing systems have been developed as a result of the rapid development which has taken place in the information industry in recent years. Methods of recording and apparatus compatible with these information processing systems have been developed and adopted. Thermal transfer recording methods, as one of recording methods of this type, involve the use of, an apparatus which is light and compact, with which there is low noise during operation, and which has excellent operability and maintenance characteristics. Moreover, since they also allow coloring to be achieved easily, these methods are the most widely used. Thermal transfer recording methods can be broadly classified into two types, namely, thermofusion types and thermomobile types. In the latter case, a thermal transfer dye providing material which has, on a support, a dye providing layer which contains a binder and a thermomobile dye is laminated with a thermal transfer image receiving material, heat is applied from the support side of the dye providing material, the thermomobile dye is transferred to the recording medium (thermal transfer image receiving material) in the form of a pattern corresponding to the heat pattern which has been applied and an image is formed in this way.
Moreover, a thermomobile dye is, for example, a dye which can be transferred from a thermal transfer dye providing material to a thermal transfer image receiving material by sublimation or diffusion in a medium.
However, the following disadvantages are encountered with thermal transfer image receiving materials for use in the thermomobile type thermal transfer recording method.
The polymers used in the receiving layer for the thermomobile dye are soluble in organic solvents and so an organic solvent system is used for the receiving layer coating liquid. Furthermore, the apparatus and vessels used in the manufacturing process must be cleaned with organic solvents. Hence, the apparatus used for preparing the coating liquid and the coating apparatus must be explosion-proof. Furthermore, organic solvents are very expensive when compared to water and so the production costs are increased. Moreover, problems can arise with respect to the health of the operators.
Various attempts have been made to obtain a high transfer density and high sensitivity in the thermal-mobile type thermal transfer recording method. However, these methods have various problems.
(1) Method wherein dye accepting polymers with a low glass transition point is used
This method has problems in that when the dye accepting polymer has a glass transition point which is at room temperature or lower to obtain sufficient density, the transferred image is faded or the transferred dye is re-transferred to the contact surface (i.e., color migration by contact) when image receiving materials after transfer are placed on one another.
(2) Method wherein plasticizers such as oil capable of dissolving dyes are incorporated in image receiving layers, etc.
This method has problems such as fading of the transferred image with the passage of time, and re-transfer as in the above method (1). Further, this method has the problem in that sticking (blocking) is liable to be caused when raw image receiving materials prepared in this method are placed on one another and stored.
(3) Method wherein a porous layer containing porous particles, etc. is provided as a low thermal conductive layer to prevent heat from diffusing during thermal transfer and to raise the temperature of transfer surface
This method has a problem in that gloss on the surfaces of the image receiving materials is reduced.
(4) Methods wherein synthetic paper having voids is used as a support
This method has problems in that curling is liable to be caused after thermal transfer and the costs of the materials are high.
(5) Method wherein the amount of dye in the dye providing layers of the dye providing materials is increased
This method has problems in that when the dye providing materials are stored over a long period of time, the dyes migrate to the back side of the support or are precipitated out on the surfaces thereof to thereby cause lowering or unevenness in the contents.
(6) Method wherein voltage to be applied to thermal head is elevated
This method has problems in that the life of the thermal head is shortened and the heat fusion of the image receiving material to the dye providing material is likely to occur.
Accordingly, the present invention is intended to solve the above-described problems which are caused when the dye accepting substances are coated as organic solvent solutions.